$A$ block $P$ of mass $M_P$ is in contact with another block $Q$ of mass $M_Q$ as shown in the figure and they are placed on a smooth floor. Find the force on block $Q$.

$A$ balloon of mass $M$ descends with an acceleration $a (< g)$. What mass needs to be removed from the balloon so that it starts ascending with acceleration $a$?

$A$ block of mass $m$ slides down on a wedge of mass $M$ as shown in the figure. Let $\vec a_1$ be the acceleration of the wedge and $\vec a_2$ be the acceleration of the block with respect to the ground. $N_1$ is the normal reaction between the block and the wedge,and $N_2$ is the normal reaction between the wedge and the ground. Friction is absent everywhere. Select the incorrect alternative.

An $80\, kg$ person is parachuting and is experiencing a downward acceleration of $2.8\, m/s^2$. The mass of the parachute is $5\, kg$. The upward force on the open parachute is ........... $N$ (Take $g = 9.8\, m/s^2$)

Two rectangular blocks of masses $40 \ kg$ and $60 \ kg$ are connected by a string and kept on a frictionless horizontal table. If a force of $1000 \ N$ is applied on the $60 \ kg$ block away from the $40 \ kg$ block,then the tension in the string is: (in $N$)

$A$ monkey of mass $20 \, kg$ climbs up a rope which can withstand a maximum tension of $25 \, kgf$. What is the maximum acceleration with which the monkey can climb up? (Take $g = 10 \, m/s^2$)